Device for securing an implant

ABSTRACT

The invention relates to a self-retaining implant for fixing a bone cover or a bone fragment in an opening in a skull bone. The implant comprises a support element with an upper side and an lower side facing the bone cover. Arranged on the lower side of the support element is an extension, which supports a spike preferably extending parallel to the support element. The spike can be driven laterally into the bone cover or bone fragment by means of a driving-in device according to the invention. The driving-in device according to the invention comprises a receiving element for the implant. A driving-in mechanism for driving the implant into the bone cover or bone fragment can be coupled with the receiving element.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The invention relates to an implant for attaching a bone cover or bonefragment, and more particularly for fixing a bone cover or a skull bonefragment removed in a craniotomy to a skull cap. The invention alsorelates to a device for securing the said implant to the bone cover orbone fragment.

2. Description of the Prior Art

Within the framework of skull operations, bone covers, i.e. plate-shapedbone parts, are often sawn out of the skull bone. At the end of theoperation, it is necessary to fix these bone covers again in theresulting opening in the top of the skull, so that the bone cover canheal into its old position again. A comparable problem arises when skullbone fragments need to be fixed in the region of the top of the skull.

Various implants have been proposed for attaching bone covers or skullbone fragments. Thus, implants are known which comprise two screw holes.In a first step, implants of this type are secured by means of screws tothe bone cover, for example, which is to be fixed in place.Subsequently, the implants screwed to the bone cover are additionallysecurely screwed to the skull bone. As a result of the fact that it isfirstly necessary to secure each individual implant by means of a screwin each case to the bone cover and then to the skull bone, the fixing ofthe bone cover is very time-consuming. In order to reduce the timeoutlay associated with the fixing of a bone cover, self-retainingimplants have been proposed.

A self-retaining implant of this type is known, for example, from DE 19907 354 A1. This implant is a clamp-like element, which is placed ontothe bone cover which is to be fixed. To this end, the implant comprisestwo contact arms, which are arranged spaced apart from one another andin the fitted state of the implant engage around the bone cover. In thisrespect, the first of the two contact arms contacts the upper side ofthe bone cover and the second of the two contact arms contacts theunderside.

A disadvantage in a clamp-like implant of this type is that it isawkward to handle. The awkward handling is first and foremost a resultof the fact that different bone covers are not always of the samethickness and the thickness of a single bone cover may even vary. Afurther disadvantage is that the contact arm resting against theunderside of the bone cover rests upon the flaps of the meninges oncethe bone cover is secured and under certain circumstances may damage theflaps.

It is the object of the invention to provide an implant system whichcomprises a self-retaining implant offering simplified handling.

SUMMARY OF THE INVENTION

This object is attained according to the invention by an implant systemwhich comprises a self-retaining implant with a spike which can belaterally driven into the bone cover or bone fragment as well as adriving-in device for the said implant.

The self-retaining implant comprises a support element with an upperside and a lower side facing the bone cover or bone fragment. Arrangedon the lower side of the support element is an extension, which supportsat least one spike extending in the direction of the bone cover. Thespike is laterally driven into the bone cover or bone fragment.

According to a first variant, the driving-in device comprises aforce-transmitting element in the form of e.g. a holding or receivingelement for the self-retaining implant, as well as a driving-inmechanism, which can be coupled with the force-transmitting element, fordriving-in the implant, preferably the at least one spike of theimplant, laterally into the bone cover or bone fragment. In thisrespect, the driving-in mechanism can be coupled with a force-receivingsurface coupled with the force-transmitting element in such a mannerthat the driving-in force is transmitted by the driving-in mechanisminto the force-receiving surface, from here into the force-transmittingelement and from the force-transmitting element into the implant.According to a second variant of the driving-in device, there is nodriving-in mechanism. In this case, the driving-in force is directlyintroduced, for example by means of a hammer-like tool, into theforce-receiving surface, which is coupled with e.g. a receiving elementfor the implant in a force-transmitting manner.

The self-retaining implant according to the invention is not secured bypushing onto the bone cover, but is secured by means of one or morespikes laterally driven into the bone cover or bone fragment. Thedriving-in of the at least one spike of the implant is preferablyeffected by using a driving-in device according to the invention, whichto this end may comprise a suitable driving-in mechanism. In practice,it has been found that a driving-in of the self-retaining implant, inparticular with the use of a driving-in device according to theinvention, is particularly advantageous from the point of view ofhandling. The connection between the implant and the bone cover or bonefragment resulting from the driving of the spike of the implant into,for example, the spongy region or cortical region of the bone cover orbone fragment is extremely stable and reliable.

The at least one spike of the self-retaining implant is arrangedrelative to the support element in such a manner that it can be reliablydriven into the bone cover or bone fragment and ensures good anchoringof the implant.

To this end, the spike preferably extends substantially parallel to thesupport element. However, the spike may also be inclined relative to thesupport element, so long as the spike can be driven in to a sufficientdepth. The transition between the extension and the spike arranged onthe extension may be continuous, so that no defined border is visiblebetween the extension and the spike. However, according to a preferredembodiment, the spike projects from the extension at an angle of, forexample, 90°.

The extension expediently forms an angle of between 45° and 135° withthe implant element. Preferred is an extension which extendssubstantially at right angles to the support element. In this case, theextension can function as an abutment, which allows for precisedriving-in of the spike. In other words: as soon as the extension comesto rest against lateral regions of the bone cover or bone fragment, itprevents further driving-in of the spike. In addition, an analysis ofthe position of the extension relative to a lateral region of the bonecover or bone fragment provides a visual assessment as to whether thespike of the implant has been driven in to a sufficient depth.

According to a preferred embodiment, the extension is arranged relativeto the support element in such a manner that the support element and theextension essentially form a T-shaped structure in cross section. Inthis respect, the support element corresponds to the cross beam of the Tand the extension corresponds to the longitudinal beam thereof. Theextension thus divides the support element into two support armsextending in opposite directions. The first of the two support armsextends in the direction of the bone cover or bone fragment and thesecond of the two support arms in the direction of the skull bone. Thistype of design of the implant is advantageous, since the support armextending in the direction of the bone cover, for example, and restingupon the upper side of the bone cover, together with the spike driveninto the bone cover, allows for particularly reliable securing of theimplant to the bone cover. In addition, the support arm cooperating withthe bone cover can be advantageously used as a guide during thepositioning and driving in of the implant.

It is, however, also possible to dispense with the support armcooperating with the bone cover or bone fragment. Thus, instead ofhaving a T-shaped design, the implant could also have a Z-shapedstructure, for example, the upper cross beam of the Z functioning as asupport element on the skull bone and the lower cross beam forming thespike.

The support element preferably has a flat, e.g. strip-shaped form. Theunderside of the support element can be concave or spherically curved atleast in sections in order to ensure good adaptation of the implant tothe curvature of the skull. Expediently, the support element of theimplant is flexible at least in certain regions, in order to allow forindividual adaptation of the implant to the curvature of the skull.

The spike of the implant which is to be driven in is arranged, forexample, at an end of the extension remote from the support element. Thespike can be designed in various ways. Thus, it is possible, forexample, to provide a spike in the form of one or more spurs or a sawtooth structure. However, the spike preferably has a flat, triangularstructure. In order to facilitate the driving-in of the spike, the spikecan be provided with sharpened edges. The length of the spike can befreely selected within a wide range, so long as sufficiently reliableanchoring of the implant is guaranteed.

At its end opposite the spike, the support element may comprise a screwhole to allow for fixing of the bone cover or bone fragment providedwith one or more implants to the skull bone by means of screws. In thecase of a support element with two or more support arms, the screw holeis consequently constructed in the support arm which cooperates with theskull bone. The support element preferably has a locally increasedthickness in the region of the screw hole. In this respect, thethickness of the support element in the region of the screw hole can beselected in such a manner that the screw head can be partially or fullyrecessed in the screw hole. This is advantageous for cosmetic reasons.In contrast, in the region of the support element outside the screwhole, the thickness of the support element can be markedly reduced. Theinterior of the screw hole is expediently spherically curved in order toallow for the recessing of bone screw heads having a correspondingspherical curvature.

The implant according to the invention can be driven into the bone coveror bone fragment in different ways. This is possible in a particularlysimple manner using the driving-in device according to the inventioncomprising a driving-in mechanism. The driving-in mechanism can beconstructed in such a manner that it allows for the application of astriking force upon a receiving or holding element provided for theimplant. To this end, the driving-in mechanism can comprise a strikingelement, which is displaceable against a spring force. By means of thespring force, the striking element can be prestressed in the driving-indirection, the striking force being actuated by a sudden reduction inthe prestressing.

The striking element is preferably formed by a first carriage guidedcoaxial to the receiving element. Guidance for the first carriage can beformed, for example, by a bolt arranged coaxial to the receivingelement. The receiving element can be connected to the bolt or anotherstationary component of the driving-in device in such a manner that thereceiving element is displaceable in the axial direction to a limiteddegree.

The driving-in device expediently comprises an operating mechanism forthe driving-in mechanism. In the case of a driving-in mechanism whichcomprises a striking element displaceable against a spring force, theforce required for the displacement of the striking element ispreferably applied by means of the operating mechanism. To this end, theoperating mechanism can be actuated with the aid of an electric motor orone or more fingers.

For the coupling of the operating mechanism with the striking element,i.e. for the prestressing of the striking element, for example, acoupling device can be provided. The coupling device comprises a driver,for example, for taking along the striking element. In cases where acoupling device is present, a corresponding decoupling device isexpediently provided, which allows for a decoupling of the operatingmechanism and striking element in order to activate the striking force.

According to a particularly preferred embodiment, the driving-in deviceaccording to the invention has a gun-like construction. This type ofdesign allows for particularly ergonomic and reliable driving in of theimplants. Other designs of the driving-in device according to theinvention are, however, also conceivable. Thus, the driving-in devicecan have a substantially cylindrical form, for example.

A driving-in device having a gun-like design typically comprises a gunbody and a gun barrel. The gun body can comprise a gun handle as well asa housing connected to the handle for accommodating the driving-inmechanism. The operating mechanism for the driving-in mechanism can beconstructed as a finger-operated gun trigger. The gun trigger ispreferably coupled with a second carriage displaceable against a springforce. In this case, the coupling device described above can befunctionally arranged between the first and second carriages.

In the case of a gun-like design of the driving-in device, it ispossible to arrange the receiving element for the implant in the mannerof a piston barrel in relation to the gun body. This type of arrangementof the receiving element allows for particularly simple positioning ofthe implant, which is to be driven into place, relative to the bonecover or bone fragment.

The receiving element can be provided with a self-locking mechanism forthe implant, so that the implant can be removed directly from thecartridge provided for the implant by means of the driving-in device. Itis therefore unnecessary to touch the implant with the fingers duringthe entire securing procedure of the implant. This is desirable forergonomic reasons.

DESCRIPTION OF THE DRAWINGS

An embodiment of the implant and an embodiment of the device will beexplained in further detail in the following with the aid of severaldrawings, in which:

FIG. 1 is a side view of an embodiment of the implant according to theinvention;

FIG. 2 is a plan view of the underside of the implant according to FIG.1 facing the bone plate;

FIG. 3 is a sectional view through the support element of the implantaccording to FIGS. 1 and 2 in the region of a screw hole;

FIG. 4 is a side view of a first embodiment of a driving-in deviceaccording to the invention;

FIG. 5 is a longitudinal section through the driving-in device accordingto FIG. 4;

FIG. 6 is a cross section through the driving-in device according toFIG. 4 along the line VI-VI according to FIG. 5;

FIGS. 7 a and 7 b are a plan view and sectional view respectively of thereceiving element for the implant;

FIG. 8 is a plan view of a second embodiment of a driving-in deviceaccording to the invention; and

FIG. 9 is a perspective view of the driven-in implant according to FIG.1 following its securing in the skull bone.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 is a side view of an embodiment of a self-retaining implant 10according to the invention. The implant 10 comprises a support element12, an extension 14 connected to the support element 12 and a flat spike16 connected to the extension 14.

The support element 12 comprises an upper side 18 and a lower side 20.Following implantation, the lower side 20 contacts a bone cover or bonefragment, not shown in FIG. 1, as well as a skull bone, also not shownin FIG. 1. In order to ensure a implant of the lower side 20 which is asfree of clearance as possible, the lower side 20 is spherically curved.The radius of curvature R measures 79.5 mm.

The support element 12 according to FIG. 1 is formed by two support arms22, 24. In the implanted state of the implant 10, the left support arm22 in FIG. 1 rests upon the skull bone and the right support arm 24 inFIG. 1 rests upon the bone cover, for example. The length ratio betweenthe left support arm 22 and the right support arm 24 can be varied bymeans of the position of the extension 14 relative to the two supportarms 22, 24. In the illustration according to FIG. 1, the left supportarm 22 has a somewhat greater length than the right support arm 24.

The left support arm 22 is provided at its end remote from the spike 16with a screw hole 26. In the region of the screw hole 26, the supportelement 12 has its maximum thickness d of approximately 0.5 mm. Thisthickness has been selected in order to allow for a cosmeticallyadvantageous recessing of a bone screw head in the support element 12.In regions remote from the screw head 26, the support element 12 has areduced thickness of, typically, 0.3 mm. This reduced thickness isselected in such a manner that the support element can be slightly bentin regions outside the screw hole. By bending the support element 12,the lower side 20 can be individually adapted to the curvature of thebone cover or skull bone.

The extension 14 of the implant 10 is secured to the lower side 20 ofthe support element 12 and extends substantially at right angles to thesupport element 12. Together, the support element 12 and the extension14 form a T-shaped structure. In this respect, the support element 12represents the cross beam of the T-shaped structure and the extension 14the longitudinal beam.

The width b of the extension 14 needs to be small, so that the bone gapbetween the bone cover or the bone fragment and the skull bone can bekept to a minimum. The widths b are expediently less than onemillimetre, for example 0.6 mm. By means of the implant 10, the bonecover or bone fragment can be positioned in the skull bone in such amanner that the bone gap along the contour of the bone cover or bonefragment is constant. However, in order to ensure faster growth of thebone cover or bone fragment, the bone cover or bone fragment can also befixed by means of the implant 10 in such a manner that it has contactwith the skull bone in certain areas.

When the support element 12 or the extension 14 is loaded with thedriving-in force, which acts to the right in FIG. 1, the driving-inforce is to be transmitted from the extension 14 to the spike 16. Thespike 16 is constructed at the end of the extension 14 lying oppositethe support element 12. It can be clearly seen in FIG. 1 that the spikeextends perpendicular to the extension 14 and substantially parallel tothe support element 12. The thickness s of the spike 16 graduallydecreases as its distance from the extension 14 increases. The edges 28,30 of the spike 16 are sharpened in order to facilitate the driving ofthe spike into the bone cover or bone fragment.

In FIG. 2, the implant 10 according to FIG. 1 is shown in a plan view ofthe underside 20 of the support element 12. As can be seen in FIG. 2,the support element 12 comprises a substantially strip-shaped form withrounded ends. The spike 16 is flat and triangular in design and cantherefore be fitted with a comparatively low driving-in force.Alternative designs of the spike 16 are also conceivable. Thus, thespike 16 could be additionally provided, for example, with barb-likestructures in order to improve the anchoring of the spike 16 in thespongy region.

FIG. 3 is a section through the implant illustrated in FIG. 2 in theregion of the screw hole 26. The interior of the screw hole 26 comprisesa spherically curved region 32, which in the direction of the underside20 opens into a short, cylindrical region 34. The spherically curvedregion 32 allows correspondingly shaped bone screw heads to be recessedin the support element 12.

The implant 10 according to FIGS. 1 to 3 is self-retaining, since it canbe secured without securing elements such as screws, nails, etc. to abone cover, for example. In contrast to the clamp-like implants of thestate of the art, the retaining force of the implant 10 is substantiallyindependent of the thickness of the bone cover. It is therefore possibleto ensure a secure anchoring of the implant according to the inventioneven in the case of small bone cover thicknesses. The implant 10 isdriven laterally into the bone cover or into the bone fragment. Theanchoring of the implant 10 therefore requires no elements restingagainst the underside of the bone cover or bone fragment, so that damageto the meninges flaps by the implant 10 is ruled out.

The length of the extension 14, i.e. the distance between the spike 30and the support element 12, is typically selected in such a manner thatthe implant 10 can be securely anchored in the case of bone coverthicknesses up to 3.5 mm. By preparing implants 10 with shorterextensions 14, it is also possible to fix bone covers with a thicknessof less than 3.5 mm. The implant 10 is manufactured from biocompatibleTiAl6V4. However, the implant 10 can also be made entirely or partiallyof a reabsorbable material instead of a metal.

FIG. 4 shows a first embodiment of a driving-in device 40 according tothe invention for the implant 10 according to FIGS. 1 to 3. Thedriving-in device 40 has the form of a gun with a gun body 42 and a gunbarrel 44. The gun barrel 44 is formed by a receiving element 46 forholding the implant which is to be driven into place. The gun body 42 isformed by a handle 48 and a housing 50.

Arranged within the housing 50 is the driving-in mechanism, not shown inFIG. 4, which cooperates with the receiving element 46. The driving-inmechanism allows for the introduction of driving force into thereceiving element 46.

The housing 50 comprises two laterally arranged and fully detachablehousing covers. In the view according to FIG. 4, a single housing cover52 can be seen. The detachable housing cover allows for easy cleaningand lubrication of the driving-in mechanism following the operation.

For the actuation of the driving-in mechanism, an operating mechanism inthe form of a gun trigger 54 is provided. The gun trigger 54 has anergonomic shape, which is adapted to actuation by means of index fingerand middle finger or by means of middle finger and ring finger.

FIG. 5 is a longitudinal section through the driving-in device 40according to FIG. 4 and in particular the driving-in mechanism 56 of thedriving-in device 40.

The driving-in mechanism 56 is constructed as a striking mechanism andcomprises a striking element in the form of an upper carriage 58. Theupper carriage 58 comprises a central through aperture 59, through whicha stationary, upper guide bolt 60 extends, which is anchored on thehousing 50. The upper carriage 58 is displaceably guided by means of aball implant 62 along the upper guide bolt 60.

The upper guide bolt 60 is radially enclosed on its outside by a helicalspring 64, which in the starting position of the driving-in mechanism 56illustrated in

FIG. 5 rests with one end against the housing 50 and with its other endagainst the upper carriage 58. During a movement of the carriage alongthe upper guide bolt 60 to the left in FIG. 5, the helical spring 64 iscompressed.

At the same time, the upper carriage 58 is prestressed to the right inFIG. 5, i.e. in the driving-in direction.

The upper guide bolt 60 projects in the manner of a gun barrel partiallyout of the housing 50. At its end projecting from the housing 50, theupper guide bolt 60 is coupled with the receiving element 46 for theimplant radially enclosing the said end on the outside. The coupling ofthe upper guide bolt 60 with the receiving element 46 is effected bymeans of a cross bolt 66 rigidly connected to the upper guide bolt 60.The cross bolt 66 projects through an opening 68 in the receivingelement 46. The opening 68 is a slot having an oval shape and thereforeallows for limited movement of the receiving element 46 relative to theupper guide bolt 60 along the axis A. The relative displaceability ofthe receiving sleeve is necessary in order to transmit the strikingforce introduced into the receiving sleeve 46 to the implantaccommodated by the receiving element 46 and not illustrated in FIG. 5.The striking force is introduced into the receiving element 46 by meansof the upper carriage 58 arranged coaxial to the receiving element 46.

Arranged within the housing 50 somewhat below the upper guide bolt 60 isa central guide bolt 70. The central guide bolt 70 is secured in astationary manner in the housing 50 and extends parallel to the upperguide bolt 60. A lower carriage 72 is displaceably guided by a ballimplant 74 along the central guide bolt 70, which penetrates the lowercarriage 72. The central guide bolt 70 is enclosed radially on itsoutside by a helical spring 76, which is supported at one end againstthe housing 50 and at its other end against the lower carriage 72.During a displacement of the lower carriage 72 along the central guidebolt 70 to the left in FIG. 5, the helical spring 76 is compressed. Atthe same time, the lower carriage 72 is prestressed to the right in FIG.5.

The lower carriage 72 is rigidly coupled with the gun trigger 54. Uponactuation of the gun trigger 54, i.e. during a displacement of the guntrigger 54 to the left in FIG. 5, the lower carriage is therefore alsodisplaced to the left. Pressed into the gun trigger 54 is a plasticsmaterial plug 82. Upon actuation of the gun trigger 54, the plasticsmaterial plug 82 comes to rest against the gun handle 48 and therebylimits the displaceability of the gun trigger 54.

At its lower end in FIG. 5, the gun trigger 54 is connected to a lowerguide bolt 76, which is displaceable relative to the housing 50. Thelower guide bolt 76 is displaceably guided along an axis B in a blindbore 78 constructed in the piston handle 48. In order to reduce thefrictional resistance, a plastics material sleeve 80 is pressed into theblind bore 78 which lines the blind bore 78 radially on the inside.

Provided within the housing 50 is a coupling device 84. The couplingdevice 84 allows for the coupling of the operating mechanism, i.e. thegun trigger 54, with the striking element in the form of the uppercarriage 58. The coupling device 84 comprises a driver 86, which ispivotable in the plane of the drawing, a leaf spring 88 and a couplingelement 90.

The driver 86 is pivotably secured to the lower carriage 72 and isprestressed in the direction of the upper carriage 58 by the leaf spring88, which is also secured to the lower carriage 72. Arranged on theupper carriage 58 is the coupling element 90 cooperating with the driver86.

Also accommodated within the housing 50 is a decoupling device 92, whichcan cooperate with the coupling device 84 and can release the couplingbetween the gun trigger 54 and the upper carriage 58. The decouplingdevice 92 comprises a pin 94 projecting into the housing 50. In order torender the decoupling threshold adjustable, the pin 94 is displaceablealong its longitudinal axis C. To this end, the pin 94 comprises anexternal thread 96 radially on its outside, which cooperates with amatching internal thread 97 in the gun body 42. A counter nut 98 allowsfor locking of the pin 94 in a desired, axial position. At its endremote from the pin tip, the pin 94 is provided with an internal polygonallowing for the application of a tool to the pin 94 in order to adjustthe decoupling threshold.

FIG. 6 is a cross section through the driving-in device 40 shown in FIG.4 taken along the line IV-IV according to FIG. 5. As can be seen in FIG.6, the housing 50 is closed laterally by two removable housing covers52, 52′. Arranged within the housing 50 is the driving-in mechanism withthe upper carriage 58 guided along the upper guide bolt 60 and the lowercarriage 72 guided along the central guide bolt 70. The lower carriage72 is connected by means of a screw 102 to the gun handle 54. The screw102 comprises an internal polygon 104. It can be clearly seen in FIG. 6that the driver 86 of the coupling device 84 cooperating with the leafspring 88 comprises a U-shaped groove 106. By means of this groove 106,the coupling device 84 cooperates with the pin 94 of the decouplingdevice. The groove 106 is arranged relative to the plane of the drawingin such a manner that the driver 86 can be forced downwards in FIG. 6 bythe tip of the pin 94 against the spring force of the leaf spring 88.

FIGS. 7 a and 7 b show the receiving element 46 of the driving-in device40 illustrated in FIG. 4. Visible is the oval opening 68, in which thecross bolt 66 illustrated in FIG. 5 is displaceably guided. Thereceiving element 46 is partially constructed in the manner of a sleeveand comprises a blind bore 108 for receiving an end region of the upperguide bolt 60 illustrated in FIG. 5. At its end lying opposite the blindbore 108, the receiving element 46 comprises a sleeve 112, whichradially encloses the cylindrical base element of the receiving element46 on the outside. Formed between the cylindrical base element of thereceiving element 46 and the sleeve 112 is a flat slot 114, which isused to receive the implant. The slot 114 can be seen in the sectionalview according to FIG. 7 b.

Arranged in the region of the slot 114 is a self-locking mechanism 110.The self-locking mechanism 110 comprises a ball 116 and a spring 118prestressing the ball 116 in the direction of the slot 114. The ball 116cooperates with the screw hole 26 of the implant 10 illustrated in FIG.2.

The method of operation of the driving-in device 40 described above withreference to FIGS. 4 to 7 b will be explained in further detail in thefollowing.

In a first step, the implant 10 illustrated in FIGS. 1 to 3 isintroduced with its left support arm 22 comprising the screw hole 26into the slot 114 of the receiving element 46. As soon as the screw hole26 lies in the region of the ball 116 prestressed in the direction ofthe slot 114, the ball 116 engages in the screw hole 26 and theself-locking mechanism 110 is actuated. Since the ball 116 engages withprestressing in the screw hole of the implant, it is no longer possiblefor the implant to accidentally slide out of the slot 114.

The implant is preferably directly removed from an implant container bymeans of the driving-in device 40. It is therefore unnecessary tointroduce the implant into the slot 114 with the aid of the fingers. Inthis manner, the handling of the implant system according to theinvention, comprising implant and driving-in device 40, is considerablyimproved.

Once the implant has been introduced into the slot 114 and has beensecured there against falling out by means of the self-locking mechanism110, the secured implant is positioned by means of the driving-in device40 in the region of the bone cover or bone fragment which is to be fixedin place. The positioning is effected in such a manner that theright-hand support arm 24 of the implant 10 illustrated in FIG. 1 comesto rest upon the surface of the bone cover or bone fragment and thespike laterally contacts the spongious or cortical region.

Subsequently, the gun trigger 54 is displaced to the left in FIG. 5 bymeans of two fingers. This movement of the gun trigger 54 is alsotransmitted to the lower carriage 52 rigidly coupled with the guntrigger 54.

Consequently, the lower carriage 52 moves to the left in FIG. 5 againstthe spring force of the helical spring 76.

As a result of the displacement of the lower carriage 72 to the left inFIG. 5, the driver 86 contacts the coupling element 90 of the uppercarriage 58. As soon as the driver 84 contacts the coupling element 90,the upper carriage 58 is taken along by the driver 86 and is alsodisplaced to the left in FIG. 5 against the spring force of the helicalspring 64.

The coupling of the lower carriage 72 with the upper carriage 58 isrecognized by the user of the driving-in device 40 in that the forcerequired for the actuation of the gun trigger 54 increases. Thisincrease in force results from the fact that it is now not onlynecessary to compress the lower helical spring 76, but also the upperhelical spring 84, owing to the coupling of the lower carriage 72 andthe upper carriage 58.

After a certain degree of displacement of the two carriages 72, 58, thepin 94 comes into contact with the groove 108 of the driver 86illustrated in FIG. 6. With a further displacement of the two carriages58, 72 to the left in FIG. 5, the driver 86 is now pivoted downwards bythe inclined surface of the tip of the pin 94 about its pivot axis 120illustrated in FIG. 5 against the spring force of the leaf spring 88.Finally, once a threshold pivoting angle is reached, the couplingbetween the driver 86 and the coupling element 90 of the upper carriage58 is abruptly released. As a result of the decoupling of the lowercarriage 72 and upper carriage 58, the upper carriage 58 prestressed tothe right in FIG. 5 by the helical spring 64 is accelerated to the rightin FIG. 5 along the upper guide piston 60. The accelerated uppercarriage 58 comes into striking contact with the end face facing theupper carriage 58 of the receiving element 46, which has been slightlydisplaced along the axis A, and exerts a blow to the said end face.

This blow is transmitted to the implant 10 arranged in the slot 114, thespike 16 of the implant 10 thereby being laterally driven into the bonecover or bone fragment. During the driving-in, the implant arm 24 of theimplant 10 resting upon the bone cover or bone fragment acts as a guide.

As soon as the upper carriage 58 is decoupled from the lower carriage72, the gun trigger 54 can be released again. Following the release ofthe gun trigger 54, the compressed helical spring 76 expands again andthe gun trigger 54 is moved by the helical spring 76 back into thestarting position illustrated in FIG. 5. The driving-in proceduredescribed above can then be repeated, if necessary, to drive the spike16 of the implant 10 deeper into position. As soon as the extension 14rests laterally against the bone cover or bone fragment, the driving-inprocedure is complete. The extension 14 then functions as a mechanicalabutment, which prevents the spike 16 from being driven too deeply intothe bone cover.

It is usually necessary to position three to four implants 10 accordingto FIGS. 1 to 3 in a bone cover in order to reliably fix the bone coverin the skull bone. Once the required number of implants have been driveninto the bone cover, the bone cover is positioned in the correspondingopening in the skull bone and is secured to the skull bone by means of abone screw for each implant. This is illustrated in further detail inFIG. 9, which will be described in more detail below.

FIG. 8 shows a second embodiment of a driving-in device 40 according tothe invention for driving an implant laterally into a bone cover or bonefragment. The driving-in device 40 has an elongated structure andcomprises a receiving element 46 for the implant as well as a knob-likeforce-receiving structure 120 having a spherically curvedforce-receiving surface 122. The driving-in device 40 also comprises asubstantially cylindrical body 124, which is arranged in aforce-transmitting manner between the force-receiving structure 120 andthe receiving element 46 for the implant. At its end facing thereceiving element 46, the cylindrical element 124 comprises a grip 126,which radially encloses the outside of the cylindrical body 124. Thegrip 126 is coupled to the body 124 so as to be immovable in the axialdirection. The receiving element 46 comprises the self-locking mechanismillustrated in FIGS. 7 a and 7 b for the implant.

In order to secure the implant to a bone plate, for example, the implantis firstly fixed in the region of the receiving element 46 by means ofthe self-locking mechanism. The implant is then positioned as describedabove and a striking force is introduced into the force-receivingsurface 122 of the force-receiving structure 120 by means of a hammer,for example. The striking force is transmitted from the force-receivingstructure 120 via the body 124 and the receiving element 46 to theimplant 10, which is thereby driven laterally into the bone cover.

FIG. 9 shows a bone cover 130, which comprises an upper bone plate 132(first cortical layer), a lower bone plate 134 (second cortical layer)as well as a spongious region 136 arranged between the upper bone plate132 and the lower bone plate 134. The implant 10 has been secured to thebone cover 130 by means of the driving-in device 40 described withreference to FIGS. 4 to 7 b. The spike 16 of the implant 10 has beendriven into the spongious region 136 of the bone cover 130 to such adepth that the extension 14 rests laterally against the bone cover 130.

Following the securing of a plurality of implants 10 to the bone cover130, the bone cover 130 was positioned in the corresponding opening inthe skull bone 140. In this respect, the underside of the support arm 22of the implant 10 comes to rest against the upper bone plate 142 of theskull bone 140. The skull bone 140 also comprises a spongious region146, which is arranged between the upper bone plate 142 and a lower boneplate 144.

Following the positioning of the bone cover 130 provided with theimplant 10 in the opening of the skull bone 140, the bone cover 130needs to be fixed in position within the opening of the skull bone 140.To this end, the implants 10 are secured to the skull bone 140 by meansof bone screws 150. During this process, the spherical head 152 of eachbone screw 150 is fully recessed within the screw hole of the implant10.

In the case of bicortical bones such as the bone cover 130 illustratedin FIG. 9, it is expedient to drive the spike 16 of the implant 10 intothe spongious region arranged between the two cortical layers. However,the driving of the spike 16 into a cortical layer is also possible andmight even be essential, e.g. in the case of mono-cortical bones.

1-12. (canceled)
 13. A device for securing a self-retaining implant to abone cover or bone fragment, wherein the implant is of the type having asupport element, an extension extending therefrom, and a spike affixedto the extension, the device comprising: a receiving element defining aslot at one end thereof for receiving at least a portion of the implant;and a driving-in mechanism coupled to the receiving element for drivingthe implant, laterally into the bone cover or bone fragment.
 14. Thedevice according to claim 13, wherein the receiving element includes anend such that a striking force can be applied to the end by means of thedriving-in mechanism.
 15. The device according to claim 14, wherein thedriving-in mechanism comprises a striking element displaceable against aspring force.
 16. The device according to claim 15, wherein the strikingelement is a first carriage guided coaxial to the receiving element. 17.The device according to claim 13, wherein the driving-in mechanismfurther comprises an operating mechanism, for selective coupling anddecoupling with the striking element.
 18. The device according to claim17, wherein the driving-in mechanism further comprises a coupling deviceinterposed between the operating mechanism and the striking element, thecoupling device normally biased for coupling the operating mechanismwith the striking element.
 19. The device according to claim 18, whereinthe driving-in mechanism further comprises a decoupling device fordecoupling the coupling device of the operating mechanism from thestriking element.
 20. The device according to claim 13, wherein thedevice is includes a pistol grip.
 21. The device according to claim 17,18, wherein the operating mechanism further includes a finger operabletrigger.
 22. The device according to claim 18, 21, wherein the fingeroperable trigger is coupled with a second carriage displaceable againsta spring force, and the coupling device couples and decouples the secondcarriage with the striking element.
 23. The device according to claim20, wherein the receiving element extends forwardly from an upper partof the pistol grip in the manner of a gun barrel in relation to a gunbody.
 24. The device according to claim 13, wherein the receivingelement further comprises a self-locking mechanism in the slot forreleasably engaging the support element of the implant.
 25. A device forsecuring a self-retaining implant of the type having a support element,an extension extending therefrom, and a spike affixed to the extensionto a bone cover or a bone fragment, the device comprising: aforce-transmitting element for cooperating with the implant; and adriving-in mechanism for applying a striking force to theforce-transmitting element in order to drive the implant into the bonecover or bone fragment.
 26. A device for securing a self-retainingimplant of the type having a support element, an extension extendingtherefrom, and a spike affixed to the extension to a bone cover or bonefragment, the device comprising: a receiving element for releasablyreceiving the implant; and a force-receiving surface coupled in aforce-transmitting manner with the receiving element for introducing adriving-in force into the implant, in order to drive the spike of theimplant, laterally into the bone cover or into the bone fragment. 27.The device according to claim 26, wherein the receiving element furthercomprises a self-locking mechanism for releasably receiving the implant.